iPhones running iOS 8.3.x and above can still use GPS apps that have full maps that are stored on the device while in Airplane mode as the device's GPS receiver does NOT get turned off in airplane mode as it did on devices running below iOS 8.3.x
So... you can use a GPS/navigation app that stores data on device when in Airplane mode, or - in places where you have no cellular or wifi available.
So... you can use a GPS/navigation app that stores data on device when in Airplane mode, or - in places where you have no cellular or wifi available.